By Jennifer L. Martin, DVM, CFDVeterinary Technology Program DirectorColby Community College

In large animal medicine, parasite resistance has become a serious issue in several species ranging from horses and cattle to small ruminants. In order to best serve our clientele, proper recommendations with regard to parasite management is essential.

Veterinary technicians routinely perform fecal examinations to assist the veterinarian in making a proper diagnosis so that he or she can prescribe the anthelmintic(s) needed to treat parasite infestations. Unfortunately, parasites are becoming increasingly resistant to several classes of these medications.

By performing two quantitative Fecal Egg Counts (FEC) using the Wisconsin Sugar Flotation Technique on an animal’s feces the day of treatment and 10-14 days after treatment with an anthelmintic, valuable information can be obtained. Five grams of fresh feces are needed and the feces must be tested within 48 hours of collection. This test is used to determine an animal’s worm burden in eggs per gram (EPG) of feces.

For horses, the client should collect one “apple” of feces so there will be a sufficient sample size for testing. Furthermore, all horses at the facility should be tested.

For cattle, the technique is the same. However, the test may be performed on a pooled sample of 20 animals. The twenty samples should be collected from random animals in the herd. The second samples do not need to be collected from the same animals. This allows the test to be performed at an affordable price as individual animal tests are not cost effective. The client should submit samples of at least 5 grams each in individual containers.

The results of these tests provide valuable information for the veterinarian to determine if treatment is necessary and whether resistance is developing to the anthelmintics used on that farm.

To perform the Wisconsin Sugar Flotation Technique, place 3 grams of feces into a paper or plastic cup. Then, add 10 ml of Sheather’s solution (Sheather’s solution is made by adding 454 grams [1 lb.] of sugar to 355 ml of hot water and stirring until dissolved. Allow the Sheather’s solution to cool prior to use and store in the refrigerator.) Mix the sample thoroughly. Place a funnel into a 15 ml centrifuge tube. Next, place a strainer into the funnel and pour the mixed solution into the strainer. Be sure to squeeze out any liquid remaining in the strainer using a tongue depressor. Centrifuge the test tube for 2-4 minutes. Then, fill the tube with Sheather’s solution until a meniscus forms. Place a coverslip on the meniscus. Let the coverslip set for 5 minutes, and then place it on a slide. Count all eggs under the coverslip using the 10x objective on the microscope. Once all of the eggs are counted, take that number and divide it by 3 to determine the eggs per gram (EPG) of feces.

Please note that when performing a FEC in horses, strongyle and ascarid eggs are counted separately. Other parasite eggs are not counted but should be noted in the results.

To perform a FEC Reduction Test (FECRT) a fecal egg count should be performed on Day 0 and again on Day 10-14. The FERCT helps the veterinarian determine the efficacy of the anthelmintic that was used.

A FECRT of 90-95% means the parasite treatment was efficacious while a FERCT of less than 90% indicates resistance.

When performing a FEC, it is important to remember that the number of eggs in the feces of ruminants varies by season. Many parasites go into developmental arrest during winter in the northern states and during summer in the southern states. So the best time of year to perform a FEC would be April through July in the northern states and December through March in the southern states. In horses, the FEC can be performed any time of the year.

In summary, the Fecal Egg Count Reduction Test using the Wisconsin Sugar Flotation Technique is simple to perform, will provide your veterinarian with a wealth of information, and adds value to your practice.